In the suit, it accuses Valeant of running a "fraudulent scheme" through its now defunct pharmacy, Philidor.

The fund says in the suit that Valeant's secret network of pharmacies used deceptive practices to sell drugs, then hid the source of these ill-gotten gains with accounting.

All of this, T. Rowe claims, was done in an effort to preserve Valeant's drug prices.

Valeant's stock has plunged around 90% since the existence of Philidor was discovered, in October. US Attorney Preet Bharara is conducting a criminal investigation into its operations, specifically into whether Philidor defrauded insurers.

Valeant is also under investigation by the Securities and Exchange Commission, and facing scrutiny from members of the US House of Representatives and Senate because of its drug pricing practices.